1. Field of the Invention
This invention relates to thermoplastic polyamide compositions, and more particularly to thermoplastic compositions comprising blends of a polyamide and an elastomer and methods of making the same.
2. Description of the Prior Art
Blends of different polymers can result in compositions which exhibit a valuable combination of properties which frequently is not obtainable by either polymer alone. However, frequently polymers are incompatible with each other and it is difficult to obtain a uniform blend and desirable properties.
There is considerable prior art related to blends of polyamides and elastomer materials. By incorporating elastomeric or rubbery materials in polyamides an improvement in the impact strength of the polyamide has been realized.
U.S. Pat. No. 4,174,358 issued Nov. 13, 1979 to B. N. Epstein discloses polyamide compositions modified with another polymer of tensile modulus less than 20,000 psi of which various elastomeric materials are exemplified. A requirement of the polymer which is dispersed in the polyamide matrix is that it be adhered to the polyamide and at least one of various adherent sites which are disclosed must be present in the polymer modifier.
In U.S. Pat. No. 3,236,914 issued Feb. 22, 1966 to J. B. Murdock et al there is disclosed an improved method for obtaining homogeneous blends of rubbery copolymers with hard saturated resinous polymers such as polyamides. The method comprises providing free carboxylic acid groups in the rubbery copolymer material whereby improved compatibility with the polyamide is attained.
In U.S. Pat. No. 4,207,404 issued June 10, 1980 to A. Y. Coran et al, homogeneous blends of nylon and chlorinated polyethylene rubber are disclosed.